JPS6221536A - Surface protective film, punching quality thereof is improved - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a bare surface protective film with improved punching processability for press Thomson blades and the like.

[Conventional technology]

Currently, synthetic resin plates commercially available for industrial use include polymethyl methacrylate, polystyrene, polycarbonate, and polyvinyl chloride, which are manufactured by extrusion molding, calendering, cast polymerization, etc., but all of them are difficult to combine with other objects. The surface of synthetic resin plates can easily be damaged by contact or friction, which can impair their appearance. A surface protection sheet such as paper or synthetic resin film is usually pasted 9 to prevent damage to the surface.

Pasting the surface protection sheet on the synthetic resin board mentioned above involves applying a water-soluble glue such as partially saponified polyvinyl acetate in the case of paper, or applying polyisobutylene in the case of synthetic resin film. It is common to apply an adhesive made of rubber, natural rubber, or acrylic rubber with a tackifier added.

However, when a surface protection sheet coated with glue, adhesive, etc. is pasted on a synthetic resin board, it has the disadvantage that when it is peeled off, it tends to leave so-called adhesive residue on the surface of the synthetic resin board. A single layer film of ethylene/vinyl acetate copolymer as described in JP-A No. 60-24944, a base material layer made of polyethylene, polypropylene, etc. as described in JP-A-60-5464. A two-layer film consisting of a temporary adhesive layer and an ethylene/vinyl acetate copolymer is now being used.

At this time, the thickness of the film made of ethylene/vinyl acetate copolymer used as the surface protection sheet was
As stated in Publication No. 7-21537, synthetic resin plates are heavy, so synthetic resin plates are often There are many chances for the surface to be damaged, therefore, if the thickness is less than 401 tm, the strength is insufficient, and if it is more than 200 μm, it is not economically viable. Therefore, the thickness is usually 40 to 100 μm.

[Problem that the invention seeks to solve]

The synthetic resin plate containing a specific sulfonate and covered with a film made of ethylene/vinyl acetate copolymer described in the above-mentioned Japanese Patent Application Laid-Open No. 60-24944 is
It maintains the initial antistatic performance and adhesive performance, but with the same treatment, the surface is covered with a film made of ethylene-vinyl acetate copolymer with a thickness of 40 to 100 μm. I created a ~0.8u synthetic resin sheet and punched it using a press, but when the synthetic resin sheet is made of inferior, hard, and brittle materials such as polymethyl methacrylate and polystyrene, the synthetic resin The punched part of the sheet may crack, delamination may occur,
Due to the whitening, it was not possible to obtain a product that was free from practical problems.

In addition, a base layer made of polyethylene, polypropylene, etc. and a vinyl acetate content of 10 as described in Japanese Patent Publication No. 60-5464.
~25% by weight of a temporary adhesive layer consisting of an ethylene-vinyl acetate copolymer, and this temporary adhesive layer is (a) disterial.
3,3'-thiodipropionate, and (b)z, 4-
A surface protective film with a thickness of 40 μm to 100 μm containing a penzoquenone ultraviolet absorber such as dihydroxybenzoquenone, whose adhesive performance does not change much even when exposed outdoors, is applied to a synthetic resin sheet with a thickness of 0.2 to 1.6 μm. I tried attaching it to the surface and punching it out using a press, but the results were similar to those mentioned above.If the synthetic resin sheet is made of a hard, brittle material such as polymethyl methacrylate or polystyrene, the synthetic resin sheet The punched portions of the resin sheet were cracked, delaminated, and whitened, so that no product with any practical problems could be obtained.

If a single-layer or double-layer surface protection film made of ethylene/vinyl acetate copolymer with a thickness of 40 to 100 μm is attached to the surface of a synthetic resin sheet, problems such as adhesive residue can be solved, but・The punching workability of Thomson blades, etc., is still lacking.

This is not completely satisfactory in practice.

[Means and effects for solving the problems] The present inventors:
As a result of intensive studies to overcome these drawbacks, we found that synthetic resin sheets are lighter in weight than synthetic resin plates, so they are easier to handle at each stage of production, storage, transportation, and molding, and are therefore easier to handle than other synthetic resin sheets. This reduces the chances of the surface being scratched by contact with other objects or friction, so the surface is protected 1! The thickness of the film can be reduced.Also, when a surface-protected synthetic resin sheet is punched using a press or Thomson blade, the synthetic resin sheet will break brittle, but the surface protection film will be elastic if the film is thick. Because it contains elements, it will eventually plastically fracture while remaining stress depending on the deformation rate, resulting in a discrepancy between the fracture speed of the synthetic resin sheet and the surface protection film. When the thickness is reduced, there is no elastic element and there is no residual stress depending on the deformation rate, resulting in plastic fracture, so the gap between the fracture speed of the synthetic resin sheet and the surface preservation film becomes slightly smaller. Furthermore, the thickness of the film made of ethylene/vinyl acetate copolymer that forms the temporary adhesion surface is 50% of the total thickness of the film.
The present invention was completed by focusing on the fact that when the film is made larger than 1, the film stretches with a small amount of stress and evenly covers the blade surface of a press punch, etc., without exerting unbalanced breaking stress on the synthetic resin sheet.

That is, in the present invention, one layer forming the back surface is made of a random copolymer of propylene and ethylene, a propylene propylene copolymer, high-density polystyrene, or a mixture of at least two of these, The other layer forming the vinegar and the content 5
A polyolefin-based two-layer film made of an ethylene/vinyl acetate copolymer of ~25% by weight, where the total thickness of the film + 15 to 35 μm The thickness of the temporary adhesion surface layer of one film is 50% or more of the total thickness. This is a surface protection film with improved punching processability.

For the layer forming the back surface used in the present invention, a known random or block copolymer of propylene and ethylene may be used. In the case of homopolymer polypropylene, it is preferable because it has poor sliding properties. MF of these copolymers
There are no particular restrictions on R as long as it can be formed into a film, but
It is usually i, o to 159710 minutes.

The high density polyethylene used in the present invention has a density o of 94
A known material having a value of ot/d or higher can be used. There is no particular restriction on the MI as long as it can be formed into a film, but it is usually 0.2.
~xor/lo lock.

Also, any known ethylene/vinyl acetate copolymer having a vinyl acetate content of 5 to 25% by weight may be used. Its MI is 1-15
Preferably, the ratio is y/lo.

In addition, the surface protection film of the present invention may include, if necessary,
Additives such as ultraviolet absorbers, heat stabilizers, antioxidants, and various fillers may be added as appropriate.

The ethylene/vinyl acetate copolymer with a vinyl acetate content of 5 to 25% by weight used in the present invention may be made of terpene resin, coumaron resin, petroleum resin, as necessary, within the range that does not adversely affect adhesive residue. You may add a tackifier such as.

The surface protection film of the present invention is generally produced by a coextrusion lamination method in which the back layer, the front layer, and the adhesion layer are melt-mixed in separate extruders and then guided to the same die to be thermally bonded and laminated. It can be manufactured using φ die method.

It is also possible to use a dry lamination method in which a back layer and an adhesive surface layer that have been previously formed into a film are bonded together, or to extrusion coat the adhesive surface layer on a back layer that has previously been formed into a film.

The synthetic resin sheet using the surface protection film of the present invention may be a non-stretched sheet or a stretched sheet, and examples thereof include sheets of polymethyl methacrylate, polystyrene, polycarbonate, polyvinyl chloride, and the like. In particular, a methacrylic resin sheet made of a composition containing polymethyl methacrylate or methyl methacrylate by weight of 50 or more is suitable.

The thickness of the synthetic resin sheet is 0.2 to 3U, and
O, 25-1.5U is preferred.

The mechanical properties of the surface protection film with improved punching processability of the present invention are not limited as long as there are no practical problems.
As shown in the figure, a film manufactured such that the relationship between the puncture impact strength and the degree of orientation is in the shaded area is preferable because it has good punching workability such as a pressed Thomson blade.

Here, the puncture impact strength is the strength measured using a puncture impact strength testing machine for plastics manufactured by Toyo Seiki, and the degree of orientation is the strength measured by the puncture impact strength tester for plastics made by Toyo Seiki. The aspect ratio of the lengths of the perpendicular long and short axes of the punched holes formed in the film is close to 1, and the mechanical properties of the film in the longitudinal and lateral directions are balanced.

If the thickness of the surface protection film of the present invention is less than 15 μm, the surface protection performance will be insufficient, and in addition, it will be difficult to uniformly adhere the film to the synthetic resin sheet, which is not preferable. It is not preferable because the punching workability of 18~
It is 30 μm.

The surface protective film may be adhered to the synthetic resin sheet on one side or both sides.

In addition, the method for adhering the surface protection film to the synthetic resin sheet is such that the layer forming the back surface is made of a random or pulsing copolymer of propylene and ethylene, a high-density polyethylene alone, or a mixture of the above-mentioned copolymer and high-density polyethylene. The other layer forming the adhesive surface has a vinyl acetate content of 5 to 25.
A polyolefin-based two-layer film consisting of ethylene/vinyl acetate copolymer with a total film thickness of 15 to 35 μm1 and a punching processability in which the thickness of the adhesive surface layer of the film is 50% or more of the total thickness. The improved surface protection film is heated to a temperature of 50°C or higher and below the melting point of the ethylene/vinyl acetate copolymer with a vinyl acetate content of 5 to 25% by weight to form the adhesive surface on the surface of the synthetic resin sheet. It is best to temporarily attach the film by pressing the sides together, but it is preferable to heat the surface protection film using a far-infrared heater, high-temperature hot air, or the like.

Alternatively, a surface protection film may be placed on a synthetic resin sheet and pressed using a four-wheel method, the synthetic resin sheet and the surface protection film may be heated and then heat-pressed by passing through a cooling roll, or the surface protection film may be subjected to corona discharge treatment, etc. The material may be oxidized by oxidation treatment and then pressure-bonded to the synthetic resin sheet using a roll or the like, but the bonding method is not limited to these methods.

The adhesion strength between the synthetic resin sheet and the surface protection film is 90
° Peel test: 30-200r/25 width, preferably 4
A width of 0 to 140f/25+++a is appropriate.

Applications of the surface-protected synthetic resin sheet include CRT covers, calculator covers, liquid crystal covers, sheets for polarizing plates, lighting covers, and various nameplates, but it is suitable for nameplates.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 A synthetic resin sheet and a bare surface preserving film as shown in Table 1 were brought into close contact with both sides of the synthetic resin sheet using a pressure bonding type masking device.

The adhesion strength between the sheet and film of this surface-protected synthetic resin sheet is 45172Svux width, and using a mechanical press equipped with a fixed stripper-type structure cutting die (clearance 5 inches), several points were cut into a rectangle of 1151uIX90ma+. It was manufactured by punching a nameplate with a round hole and a rectangular shape, but the punched part did not crack, peel, or turn white, and the brand did not pose any practical problems.

Below is the margin: Table 1 Comparative Example 1.2 Same synthetic resin sheet and surface protection film as in Example 1 (however, the thickness composition ratio of the back layer, the adhesion surface layer is the same,
The overall thickness of the film was 13μ and 40μ), and a nameplate was punched out using the same mechanical press as in the example.

The evaluation results of the adhesion strength and appearance of the nameplate were as shown in the second light.

Table 2 Example 2 A synthetic resin sheet and a surface protection film as shown in Table 3 were heated to 90°C with a far-infrared heater using a thermocompression type masking IT.
It was brought into close contact with both sides of the synthetic resin sheet through a rubber nip roll with a linear pressure of 8 Kglon.

The adhesion strength between the surface-protected synthetic resin sheet and the film is 55SF/25m5 width, and a cutting die with movable stripper type structure (clearance 51'ff: inside a rectangular area of 120 x 80 A nameplate with several round holes and a rectangular shape was punched out to produce the nameplate, but the punched part did not crack, peel, or turn white, so it was a brand with no practical problems.

Table 2 (Blank below) [Effects of the Invention] As explained above, if the surface protection film of the present invention with improved punching processability is used in a synthetic resin sheet, manufacturing, storage, and The surface of the synthetic resin sheet is not damaged during each stage of transportation, molding, etc., and it is possible to provide a synthetic resin sheet with a protected surface that is excellent in punching processability with a Shikamo press or Thomson blade. be effective.

Char impact strength, the vertical axis indicates the degree of orientation of the film.

Claims (1)

[Claims] 1. One layer forming the back surface is made of at least one member selected from the group consisting of a random or block copolymer of propylene and ethylene, and high-density polyethylene, and also forms a temporary adhesion surface. One layer of ethylene with a vinyl acetate content of 5 to 25% by weight.
A polyolefin-based two-layer film made of vinyl acetate copolymer, the total thickness of the film is 15 to 35 μm, and the thickness of the layer forming the temporary adhesion surface is 50% of the total thickness.
A surface protection film 2 with improved punching workability characterized by the above, one layer forming the back surface is made of at least one selected from random or block copolymers of propylene and ethylene, and high-density polyethylene, The other layer forming the temporary bonding surface is a polyolefin two-layer film made of ethylene/vinyl acetate copolymer with a vinyl acetate content of 5 to 25% by weight, and the total thickness of the film is 15 to 35 μm. A surface protection film with improved punching workability in which the thickness of the formed layer is 50% or more of the total thickness is combined with ethylene/vinyl acetate containing 5 to 25% by weight of vinyl acetate to form a temporary bonding surface of 50°C or higher. A method for using a surface protection film with improved punching processability, which is characterized by heating to a temperature in the range below the melting point of the polymer and temporarily bonding the temporary bonding side to the surface of a synthetic resin sheet.